Risk Predictive Markers for Severe Community-Acquired Pneumonia in Hospitalized Elderly Patients

Abstract

Background. Mortality in patients with community-acquired pneumonia (CAP) rises dramatically with increasing age. The pneumonia severity index (PSI) and CURB- 65 scale have shown lower prognostic value for death in the elderly. We sought to assess the predictive power of procalcitonin (PCT) and other biomarkers in blood to derive a severity prediction rule. Methods. From January 2010-March 2016, we conducted a hospital-based, cohort study of radiologically confirmed-CAP patients ≥50 years old (n = 867). Upon admittance, demographic, clinical data, PSI and CURB-65 scores, as well as results from blood tests were collected. Starting November 2014, blood was systematically collected to measure procalcitonin (PCT)(n = 159 patients). Outcomes were ICU admission and 30 day-mortality. Statistical analysis included principal component analysis (PCA), regression models, ROC and area-under-curve (AUC) tests. Results. Mean age was 72 years; range 50-106. During the 30-day period there were 148/867 (17%) deaths and 319/867 (37%) admissions to the ICU. For PSI class ≥IV and CURB-65 class ≥III, the respective diagnostic odds ratios (95% CI) for 30 day-mortality were 3.3 (2.1, 5.1) and 2.9 (1.9, 4.4) and for ICU admission 2.2 (1.6, 2.9) and 2.0 (1.5, 2.7). In ROC analysis for mortality prediction AUC for PSI class ≥IV and CURB-65 class ≥III were 0.65 and 0.60, respectively; for ICU admission 0.61 and 0.61. PCT ≥2 had low predictive value for death (AUC 0.60) and ICU admission (AUC 0.65) and combination of PCT to each score did not improve their prediction ability. According to PCA and regression models, odds ratios (95% CI) for death were: age >70 years (2.9 [1.5, 65.9]), hypotension (systolic <90; 2.3 [1.1, 5.2]), monocytes <1% (3.4[1.0, 11.2]), red blood cell distribution width <14.3 (2.5 [1.2, 5.5]), bicarbonate <18 (3.2 [1.7, 6.0]), lactate >1.6 (2.8[1.5, 5.3]) and glucose <80 (4.2 [1.4, 12.2]) with an AUC 0.77. Cardiac rate >100, body mass index >30, lactate >1.6 and urea >71 were good predictors for ICU admission (AUC 0.80) Conclusion. PSI, CURB-65 and procalcitonin have low predictive values for death and ICU admission in elderly patients with CAP. This study shows that frequently tested biomarkers are promising candidate predictors for severe CAP in elderly patients.